Office Facilities - Summary of Office Facilities Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Office facilities, gross	$ 133,251	$ 133,136
Less accumulated depreciation	(104,961)	(103,547)
Total	28,290	29,589
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Office facilities, gross	75,858	78,940
Leasehold improvements
Property, Plant and Equipment [Line Items]
Office facilities, gross	$ 57,393	$ 54,196